Butterfly type valves have long been known and are commonly used in industry. With a butterfly or any other type valve it is frequently desirable to expeditiously determine the integrity of the valve when it is in the closed position, that is, to determine as a certainty whether or not the valve is permitting leakage of fluid or gases past it.
In many industrial applications integrity of valve closure is assured by placing two valves in series. The valve closure members may be coupled together for simultaneous action. When the coupled valves are closed a line between the valves can then be tapped and by measuring pressure or otherwise it can be determined as a certainty that no fluid flow is taking place past the valves.
The use of series valves is an expensive procedure. Not only does it double the valve cost to provide this leakproof assurance, but the coupling of the valve for simultaneous action is an additional expense.
The present disclosure is directed towards a valve of the butterfly type having all the inherent advantages of a butterfly valve, including simplicity, economy, dependability and so forth, while at the same time providing an inexpensive means of assuring the integrity of the valve.
It is therefore an object of this invention to provide a valve of the butterfly type having economical and inexpensive means of readily indicating leakproof closure of the valve.
Another object of this invention is to provide a valve of the butterfly valve type including a valve disc having plural sealing means in combination with provisions in the valve body for venting the space between the disc seals to provide an indication of the leakproof closure of the valve.
These objects as well as other and more specific objects of the invention will be fulfilled in the following description and claims, taken in conjunction with the attached drawings.